Fire-alarm system.



J. J. MQGARTHY.

FIRE ALARM SYSTEM.

APPLICATION FILED 0012a, 1912.

Patentd July 29, 1913.

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fizz/em 1 5 w-e'zvvesses TED STAES Specification of Letters Patent.

Patented July 29, l9l3.

Application filed October 28, 1912. Serial No. 728,127.

To alt whom it may concern:

Be it known that I, J our: J. MCCARTHY, a citizen of the United States, residin at Newton, county of Middlesex, State of as- 5 sachusetts, have invented an Improvement in Fire-Alarm Systems, of which the following description, in connection with the accompanying drawing, is a specificat on, l ke characters on the drawing representlng llke 10 parts.

This invention relates to fire alarm systems which are adapted to bemused in connection with an working c1rou1t,.-such, for instance, as a lighting circuit, a bell circuit, or A5 even 30 having a signal therein, one end of which circuit is connected to one side of the workin circuit and the other end of which signa ing circuit is connected to the other side of the working circuit, and providing means 25' whereby when the temperature in the building or room reaches a redetermined point the signaling circuit w1ll be closed thereby causing the current'of the working circuit to be shunted therethrough and the alarm to be M sounded. This automatic closing of the normally-open signaling circuit is accomplished by means of a thermostatic plug connected to the working circuit at the point where it is desired to note any abnormal rise in temperature and a fuse plug which coti erates with the thermostatic naling circuit when t operates.

Referring to the drawings wherein I have lug to close t e sige thermostatic plug o illustrated one embodiment of my invention,

Figure 1 is a an electric chandelier and the wiring for and also indicating the method applying my invention thereto; 2 is an en- .partial diagram view showing there- 5 having a signal 6 therein of some suitable or usual type, that herein shown being in the nature of a bell, and I connect one end of this circuit 5 to the side 4 of the lighting circuit, as shown at 7, and I connect the other end of the signalin circuit to the side v3 of the lightin cmcuit t rough a fuse plug 8. The fuse p ug 8 is constructed so that normally the circuit 5 is open at said plug, but when the plug fuse blows then the signahng circuit becomes closed at said plug and current from the working circuit .3, 4 flow through the signaling circuit and sound the alarm 6. The construction of the plug 1s shown in Fig. 3, and it comprises a dy portion .9 carrying a fixed terminal 10 that is connected to one side .of the signalin circuit 5. This plug also contains a seconc l terminal 11 which is normally held separated from the terminal 10 by a fusible connectlon 12. The terminal 11 is shown as a pin shdehly contained in a sleeve or holder 13 and acted upon by a spring 14 which normally tends to PI'OJGCt said pin outwardly into contact with the terminal 10. The fusible connection 12 is secured at one end to the pin 11 and passes out .throu h an openin r 15 in the body 9 and is secureg to a screw s ell be screwed into a socket 1 ter terminal 18 that en t i mine-l 19 of the fuse plug, and a screw shell terminal 20 which connects with the screw shelllfi of the lug. The center terminal 18 and screw shelfterminal 20.01? the socket are connected in series in the side 3 of the work- -so that when the ,plug is in osition, as shown in Fig. 3, the side 3 o the workin circuit includes the screw shell 16, fusible connection 12, .pin 11, holder 13, center terminal 19 of the plug, center terminal 18 of the socket 17. The fusible connection 12 thus carries all the current normally used when the fixtures 2 are ch has a cone center ter- 16 formed thereon. This plugjis adapted to screw shell 20, i

lighted, and said connection is so constructed that it will carr this current without fusing.

So long as e fusible connection 12 remains intact the s'ignalin circuit 5 is open at the fuse .plug, as will be obvious. If, however, the current carried by the working circuit assumes abnormal proportions, then the fusible connection 12 becomes fused, thus allowing1 the spring 14 to force the pin 11 outwar yinto contact-with the terminal 10. When this occurs the signaling circuit is t5 larged sectional view through the thermostatic plug; Fig. 3' is an enlarged sectional view through the fuse plug.

In the drawings I have shown at 1 a chandelier having the usual lighting fixtures, 2

50 thereon.

3 and 4 designate the two sides of a working circuit which supplies electricity to the fixtures 2.

In applying my invention to an electrictfi lighting circuit I provide a signaling circuit closed and part of the working current will be shunted through said signaling circuit, thus sounding the alarm.

My complete invention includes a thermostatic plug which is set in operation when the temperature of the air adjacent said plug reaches a predetermined point and which when 0 erated causes an abnormal current to be eveloped in the working circuit. The thermostatic plug which I employ is' shown in sectional view in Fig. 2. It is formed with a screw shell 26 adapted to screw into an electric light socket and it carries two terminals 27 and 28, one of which is electrically connected to the screw shell and the other of which is connected to the center terminal 29 of the plug. The terminal 28 is herein shown as electrically connected to the screw shell through the connection 30, said terminal bein set into the porcelain base 31 and provi ed at its upper end with the forked portion 32. The terminal 27 is in the form of a resilient wire which is connected to a post 33 that is also anchored in the porcelain base 11 and is electrically connected to the central terminal 29 of the plug. Under normal conditions the resilient terminal 27 is withdrawn from the fixed terminal 28 and is held withdrawn by a fusible link 3 which may be made of any easily-fusible material. This link orconnection 34; ties the'terminal 27 to the post 33 and holds it out of contact with the terminal 28. Whenever the temperature at the plug reaches a predetermined point this fusible connection 34 will fuse or burn thereby releasing the terminal 27 and permitting it to come into contact with the terminal 28. If desired I may inclose' the terminals 27 and 28 in an outer shell 35 which may preferably be rovided with apertures so as to permit a ree circulation of air.

The terminals of the plug are connected to the two sides 3 and 4:, respectively of the working circuit, and this may be done in any suitable way as by screwing the thermostatic plug into an ordinary lamp socket 40 which is provided with the screw shell and center terminals 41 and 42, respectively, that are connected tot-he two sides of the working circuit 3 and 4 in usual manner. Under normal conditions the circuit through the thermostatic plug is open because of the fact that the terminals 27 and 28 are separated from each other. Whenever the temperature at the plug reaches a predetermined point, however, the fusible connection 34 will be fused, thus allowing the terminal 27 to close against the terminal 28. The resistance of the thermostatic plug is small so that when the circuit is closed through said plug the amperage of the working circuit will be greatly increased and increased to a sufiicient extent to fuse the connection 12. The fusing of the connection 12 will close the signaling circuit 5 as above described, thus causing the alarm to be sounded. V

With my invention it is possibleto lace a thermostatic plug in any one of the am sockets of an electric-lighting system, an

whenever the temperature of the air adjacent said plug is suflicient to cause the fusi-- ble link 34 therein to be fused, then the alarm will be set in operation to sound the alarm 6.

The alarm 6 may be placedin any location, as will be obvious.

Where several branch line circuits are taken off ,from the main line circuit an annunciator may be used in connection with the alarm 6 to indicate on which particular branch circuit the thermostatic plug has operated.

I have shown the thermostatic plugs in Fig. 1 as secured in sockets placed atthe upper end of the chandelierl, but the operation would, be the same if a thermostatic plug were placed in any one of the fixtures 2.

Havin fully described my invention, what I aim as new and desire to secure by Letters Patent is 1. In a fire alarm system, the combination with a working circuit, of a signaling circuit having one end thereof connected to one side of the working circuit, a fuse plug forming the connection between the other end of said signaling circuit and the other side of the working circuit, said fuse plug having two terminals connected in series with said working circuit, a fusible connection between said terminals, a third terminal connected to the signaling circuit and normally disconnected from the other terminals, and means to establish a connection between one of the first-named terminals and said third terminal when the fusible connection is destroyed, said fusible connection being capable of withstanding normal working current without fusing, and means for causing the production of an abnormal current in the working circuit suflicient to fuse said fusible connection when the temperature at a predetermined location increases beyond a predetermined point whereby said fusible connection will be destroyed and the signaling circuit closed.

2. In a fire alarm stem, the combination with a working circuit having lamp sockets connected therewith, of a signaling circuit having one end thereof connected to one side of the working circuit, a fuse plug forming the connection between the other end of said signaling circuit and the other side of the working circuit, said fuse plug having two terminals connected in series with said working circuit, a fusible connection between sald terminals, 9. third terminal connected to the signaling circuit and normally disconnected from the other terminals, means to establish a connection between one of the first-named terminals and said third terminal when the fusible connection is destroyed, said fusible connection being capable of withstanding normal work ing current without fusing, and a thermostatic plug adapted to be placed in any lamp socket of the lighting system and provided with two low resistance terminals normally held separated by a fusible c0n nection whereby when said connection is fused the circuit is closed through said thermostatic plug, thus producing an ab- 15 normal current in the main circuit which fuses the fusible connection of the fuse lug. In testimony whereof, I have sign my name to this specification, in the presence of two subscribing witnesses.

JOHN J. MCCARTHY. Witnesses:

LOUIS 0. SMITH, BERTHA F. HEUSER. 

